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How to Fix STL Errors

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The STL file format is the industry standard for 3D printing. It is quite common to have minor geometry issues in these files, so they need to be corrected before quoting or printing.

Error-Checking Software

One of the best free programs to use for this purpose is Netfabb Studio Basic.

Simply open your file in the program and look for a red exclamation point in the bottom right corner, as seen below:
Netfabb STL Error

Repair the File

Many minor problems can be corrected inside Netfabb, rather than editing the original CAD file.

1) Click on the red plus sign icon:
Netfabb Plus Sign

2) Click the Update button:
Netfabb Update Button
You can see that this file has 4 Border Edges and 1 Hole, both of which need to be fixed.

3) Click these repair buttons in the following order on the Actions tab:
Netfabb Repair Steps

Verify the Repairs

It is good to verify the repairs before applying them.

1) Click the Update button on the Status tab:

2) Verify that the three numbers are zero:
If they are not all zero, then more repair is needed, probably in your CAD program.
Netfabb Apply Repair

3) Verify that the repaired image looks reasonable:
There should be no yellow lines or red surfaces remaining. If they are, then more repair may be needed, probably in your CAD program.

4) Click the Apply Repair button:
See the image above. Now the red exclamation sign should be gone from the bottom right corner. If not, more repair is required, either in this program or in your CAD program. The above technique will take care of 90% of problems.

Save the Repaired File

To save your new file, click the model to select it and go to Part...Export Part...As STL.

Need to Repair a SketchUp File?

See our SketchUp Model Repair page.


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